In web technologies, what is the main difference between XML and HTML in terms of purpose and the use of tags?

Introduction / Context:
XML and HTML are both markup languages that use tags, but they were created for different purposes. XML focuses on describing and transporting structured data, while HTML focuses on presenting content in web browsers. Interview questions often ask about this distinction and about the use of user defined tags in XML versus predefined tags in HTML, because understanding these differences is fundamental to many web and integration technologies.

Given Data / Assumptions:
Both XML and HTML use angle bracket tags to mark up content.XML stands for Extensible Markup Language, and HTML stands for HyperText Markup Language.The question asks about the main difference in purpose and tag usage.We assume a general web development context where XML is used for data exchange and HTML for rendering pages.

Concept / Approach:
XML is a flexible format that allows users to define their own tags to represent domain specific data. It focuses on structure and meaning, not on how things look on the screen. HTML, in contrast, defines a set of standard tags such as p, h1, div, span, and a, which browsers interpret to render text, images, and layout. While HTML can embed data, its primary goal is presentation, and it does not allow arbitrary new tags to change semantics in the same way XML does. Styles and behavior in HTML are handled by CSS and JavaScript, whereas XML is often processed by custom applications, parsers, or transformations such as XSLT.

Step-by-Step Solution:
First, recall that XML was designed to be extensible so that developers can create custom tags suited to their data, for example invoice or customer.Next, remember that HTML comes with a fixed vocabulary of tags defined by the standard, focusing on how content is structured for display.Then, consider that XML documents are often used for configuration files, messages, and data feeds, while HTML documents are loaded by browsers for human viewing.After that, compare the answer choices and look for a statement that captures both the extensibility of XML and the presentation focus of HTML.Finally, recognize that option A describes this distinction correctly, making it the correct answer.

Verification / Alternative check:
Examples from practice include XML based formats such as RSS, SOAP, and configuration files where custom element names represent business concepts. HTML pages, on the other hand, use standard tags and rely on CSS for visual styling. Browsers do not treat arbitrary XML tags as known visual elements without additional processing. This contrast is documented in many tutorials and clearly supports the explanation in option A. None of the other options align with this well established understanding.

Why Other Options Are Wrong:
Option B reverses the roles, incorrectly claiming that HTML is for data exchange with user defined tags and XML is only for presentation. Option C asserts that both languages use the same predefined tags, which is false because XML lets users define their own tags. Option D says that neither allows user defined tags, which again conflicts with the extensible nature of XML. Option E claims that XML and HTML are identical, which ignores their different design goals and syntax rules, such as XML strictness about closing tags and case sensitivity.

Common Pitfalls:
One pitfall is to treat XML as if it were just another way to render pages in browsers, which it is not; it often requires explicit stylesheets or processing to become human friendly. Another mistake is to forget that HTML has evolved and now includes semantic tags such as header and article, but these are still predefined, not arbitrary. Developers may also mix up XML namespaces and HTML semantics. Keeping the core difference in mind, that XML is primarily for data and HTML is primarily for display, helps avoid these confusions.

Final Answer:
The correct answer is: XML is designed for storing and exchanging data with user defined tags, while HTML is designed for displaying data with predefined tags for presentation.